You have an Exchange Server 2010 Edge Transport server named Server1.

A partner organization has an Exchange Server 2010 Edge Transport server named Server2.

You need to encrypt SMTP communication between Server1 and Server2. The solution must ensure that both servers use a trusted certificate.

What should you do?

A.
Enable Domain Security authentication.

B.
Enable Exchange Server authentication.

C.
Enable Externally Secured authentication.

D.
Disable the Anonymous users permission group.